1 / 43

Extra Dimensions @ the LHC

Extra Dimensions @ the LHC. ED@LHC. M ü ge Karag ö z Ü nel Pheno Club 21 th June 2007 Oxford University. Flatland: A Romance of Many Dimensions With Illustrations by the Author, A SQUARE [Edwin Abbott Abbott]. Dedication

admon
Télécharger la présentation

Extra Dimensions @ the LHC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Extra Dimensions @ the LHC ED@LHC Müge Karagöz Ünel Pheno Club 21th June 2007 Oxford University

  2. Flatland: A Romance of Many DimensionsWith Illustrationsby the Author, A SQUARE[Edwin Abbott Abbott] Dedication ToThe Inhabitants of SPACE IN GENERALAnd H.C. IN PARTICULARThis Work is DedicatedBy a Humble Native of FlatlandIn the Hope thatEven as he was Initiated into the MysteriesOf THREE DimensionsHaving been previously conversantWith ONLY TWOSo the Citizens of that Celestial RegionMay aspire yet higher and higherTo the Secrets of FOUR FIVE OR EVEN SIX DimensionsThereby contributingTo the Enlargement of THE IMAGINATIONAnd the possible DevelopmentOf that most and excellent Gift of MODESTYAmong the Superior RacesOf SOLID HUMANITY ED@LHC

  3. Introduction • Extra Dimensions: NOT a new idea! • Kaluza and Klein tried to unify electromagnetism and General Relativity in the ‘20s by adding a 4th spatial dimension • In late ‘90s, models arose which attempt to solve the hierarchy problem (MPl >> MEW) • A lot of variations since then… Briefly introduced here • Searches at current colliders boomed as well.. Latest greatest from Tevatron • Lots of ED studies at the LHC LHC getting ready for data Reach and prospects from CMS and ATLAS • Recently newer model predictions exist Feasibility studies with interesting signatures ED@LHC

  4. Large Extra Dimensions (LED, ADD): n > 0 (n > 2), compactified, flat MPl2~Rn MSn+2 Graviton in bulk Could be as large as 0.1mm TeV-1 ED (DDG): n ≥ 1 (n = 1) MC : compactification scale Gauge bosons in bulk as well Warped Extra Dimensions (RS): n = 1, highly curved 2-branes solution: RS1 k/MPl, k: curvature, warp factor Universal Extra Dimensions (UED): n = 1, flat, MUED: only1 ED KK-number conservation MC and cut-off scale L All SM particles in the bulk Lots of KK spectra Searches Concentrated on Arkani-Hamed, Dimopoulos, Dvali Phys Lett B429 (98) Dienes, Dudas, Gherghetta Nucl Phys B537 (99) ED@LHC Randall, Sundrum Phys Rev Lett 83 (99) Appelquist, Cheng, Dobrescu Phys. Rev. D 64 (01)

  5. Bosonic KK modes: simpler signatures Virtual or resonance exchange ll  ZZ qq Large ED (ADD): • Graviton in bulk • DY interference, or missing ET ED@LHC TeV-1 ED (DDG): • Gauge Bosons and Higgs in bulk • spin-1 KK resonances • DY interference Warped ED (RS): • Graviton as narrow spin-2 resonances jet+MET +MET emission Universal ED (UED): • spin-1 KK resonances

  6. Tevatron RS Graviton in ee/gg Most stringent limits to date from colliders: • CDF: gg+ee, k/MPl= 0.1, mG >889 GeV (comb) • D0: DiEM, k/MPl = 0.1, mG >865 GeV 2007 winter results with 0.9-1.3 fb-1 • 1 fb-1 9/9/2005 • 2 fb-1 2/17/2007 ED@LHC Takes a while to post-process+ analyze… EWK excl. line Both experiments have slight excess of events below 400?

  7. RS Graviton resonance search • B(G→ZZ) = 0.05 (x2 B(G→ee)) • 4 very isolated electrons • consistent with null observation at MG > 500 GeV • not yet sensitive for limits, need more luminosity Tevatron: Other Signatures LED Graviton emission search • Monojet + MET • Bckgrnd: Z→nn+jets, W→ln+jets, QCD dijet. • Expected 819±71, Observed 779. • LEP still better at low MD and n ED@LHC LHC enters the stage…

  8. x100 • CMS: PTDR came out in 2006 • Realistic simulation, but some with low statistics due to rush! • ATLAS: PTDR dates from 1999 (bit old now!) • Currently updating reach estimates (“CSC”) • Focus on early physics (0.1 - 1 fb-1) Little Higgs Z' From Tevatron to the LHC • Tevatron’s signal is LHC’s background and calibration data • Large BSM reach increase from 2TeV to 14 TeV! ED@LHC

  9. 22 m 46 m the Detectors ED@LHC Tracker:s/pT 1.5 10-4 pT 0.005 EM Cal:/E  3%/E(GeV)  0.5% Hadron Cal:/E  100% / E(GeV)  5% Mu Spec: s/pT 5% at 1 TeV/c (from Tracker) • Inner Tracking(||<2.5, 2T solenoid) : • Silicon pixels and strips • Transition Radiation (e/ separation) • Calorimetry (||<5) : • EM : Pb-LAr, Accordion shape • HAD: Fe/scintillator (centr), Cu/W-LAr (fwd) • Muon Spectrometer (||<2.7, 4T toroid) : • air-core toroids with muon chambers • Tracking (||<2.5, 4T solenoid) : • Silicon pixels and strips • Calorimetry (||<5) : • EM : PbWO4 crystals • HAD: brass/scintillator (centr+ end-cap), Fe/Quartz (fwd) • Muon Spectrometer (||<2.5) : • return yoke of solenoid with mu chambers

  10. In 2006 Atlas In 2004 ED@LHC In 2007 All coming together, Honest! In 2007

  11. Prospects for LHC Beams ED@LHC Parasitic collisions at injection energy Cancelled.. :-(

  12. Event Yield Estimates How many events per experiment at the beginning ? l  e or  Assumed selection efficiency: W l, Z ll : 20% tt  l+X : 1.5% (no b-tag, inside mass bin) ~ 105 J/Psi  + Y ll similar statistics to CDF, D0 today ED@LHC F. Gianotti, Ichep06 10 pb-1 1 month at 1030 and < 2 weeks at 1031,=50% 1 fb-1  6 month at 1032, =50% 5 fb-1  3 month at 1032 and 3 month at 1033, =50% 100 pb-1 few days at 1032 , =50%

  13. C = 0.01 (coupling constant) First data C =0.1 Long term Dimuon Mass How well do we know the apparatus? Detector effects will need to be understood ED@LHC • Short-term (<1 fb-1) • Long term (1-5 fb-1) 5 discovery reach for RS gravitons in mm needs ~50% less data if alignment is optimal!

  14. S Ferrag Mc= 6 TeV 2,4,6 ED Mathews et al. IPPP04/70 How well do we know the theory? Theory uncertainties must be under control! For LED, PDF uncertainties claimed to cancel reach above MC=4TeV For LED, NLO corrections may be ~1.6 (applicable to RS) ED@LHC Same true for background estimations for those that cannot be measured directly from data initially…

  15. Effective s for continuum G SMint sHewett MPl ~ 1019 GeV, MPl(4+n)~MEW Large Extra Dimensions (ADD) • Flat LEDs generate tower of KK gravitons with mass splitting ~ 1/RC continuum of graviton states • Size of ED determined by the fundamental scale MD and number of ED Signatures: • Virtual production with DY interference  excess above continuum • Real graviton emission with jet or photon ED@LHC n<=2 ruled out (by Eot-Wash) MD < 1TeV ruled out by Tevatron

  16. Di-photon/dilepton invariant mass Manageable backgrounds Min invariant mass cut extends reach Signal pp→G→μμ SM Belotelov et al., CMS PTDR 2006 Virtual Exchange Searches ED@LHC Kabachenko et al. ATL-PHYS-2001-012 • 2 OS muons & Mμμ>1 TeV • Bkgrd: mainly Irreducible DY • PYTHIA + CTEQ6L, Kf=1.38 CMS 5s Sensitivity for n=6..3 • 1 fb-1: ~4.0-5.5 ТеV • 100 fb-1: ~5.5-8.2 ТеV ATLAS Sensitivity for n=5..2 100fb-1: MD ~6.3-7.9 TeV

  17. L.Vacavant, I.Hinchcliffe J. Phys G 27 (01) LED from Graviton Emission pp→jet+G Signature: high ET jet + MET (from escaping G) Bkgrnd: irreducible jet+Z/W via invisible decays ED@LHC ATLAS sensitivity in 100 fb-1 CMS sensitivity pp→g + G MD= 1– 1.5 TeV, n<7, 1 fb-1 2 - 2.5 TeV, n<7, 10 fb-1 3 - 3.5 TeV, n<6,100 fb-1 much lower rates than mono-jet signature Signature: high-pT photon + MET Bkgrnd: irreducible Z/γ → , fakes J. Weng et al. CMS NOTE 2006/129 Rates for MD≥ 3.5TeV are too low for 5σ discovery with systematics

  18. Formation MBH = √S Parton Rs Parton Webber et al, 2005 Those m-Blackholes Arise from models with ED Could be produced when ECM > MPl Need QT of gravity as MBH approaches MPl σ ~ πRS2 ~ 1 TeV-2 ~ 10-38 m2 ~ O(100)pb LHC  Black Hole Factory, rates as high as 1Hz! ED@LHC Nick Brett If the impact parameter of a 2-parton collision < Schwarzschild radius Rs, then a black hole with MBH is formed. BH from LED, possible from RS as well

  19. Distinguishing features High Multiplicity, ΣET, Sphericity, MPT Democratic Decay Theory estimates limit systematics Charybdis event generator Decay Harris, et al. JHEP05 (2005) 053 6.1 TeV MBH J. Tanaka , “Search for Black Holes”, 24/05/03 Athens m-Blackhole Detection at ATLAS BH lifetime ~ 10-27 – 10-25 seconds! Decays with equal probability to all particles via Hawking Radiation (~ a BB spectrum) evaporates into (hadron : lepton)= (5 : 1) accounting for t, W, Z and H decays ED@LHC Giddings,Thomas PRD65(2002)056010 N=6 gives a larger yield than n=2, anti-complimentary to LED! “I have never won the national lottery, so go for it!” – anony, on BH threat from LHC!

  20. Randall Sundrum (Type I) Brane metric and gravity strength scales as function of bulk position Coupling constant: c= k/MPl, k: curvature scale Well separated narrow-width graviton mass spectrum with masses mn=kxnekrcπ (J1(xn)=0) 10fb-1 100fb-1 hep-ph/0205106 TeV Planck Bulk (y) Warped Extra Dimensions ED@LHC c>0.1 actually forbidden

  21. Allanach et al, hep-ph 0006114 M=1.5, 1.75, 2 TeV No Kf for signal SM WED RS1 Searches ATLAS Spin exploitation • Use cosq* distribution of the dilepton system • Determine Spin-2 nature of graviton at 90% C.L. up to MG = 1720 GeV with 100 fb-1 CMS PTDR results • Use ll and gg: B(G->gg) = 2* B(G->ee/mm) • Reach in ee and gg similar (unmanageable gg bkgrnd) (also not enough stats) • CMS can detect at 5s up to 1.8 TeV (c=0.01) and 3.8 TeV (c=0.1) with 100 fb-1 • Uncertainties’ effect in mass ~150 GeV ED@LHC Tevatron is just sensitive to c=0.01 around 300 GeV with 1 fb-1

  22. ppZ(1 ) /g(1)e+e- Azuelos, Polesello EPJ D C39 Sup.2 (04) TeV-1 Searches in Dileptons • 1 ED with small enough compactification for gauge bosons to travel in bulk • All fermions localized at a fixed point (M1) • destructive interference with SM GB • cKK = √2 cSM • q and l at opposite points (M2) • constructive interference • V(k) appear as resonances: Mk = √(M02+k2/R2), k=1,2,… • search for anomaly/bump in dilepton invariant mass ED@LHC • ATLAS5s reach in Mll (fast simulation): MC = 5.8 TeV in 100 fb-1 • If no peak, limit ~13 TeV in 300 fb-1 • CMS5s reach in Mee (full simulation): MC = 6.0 TeV in 80 fb-1 Z(1) can be discriminated from Z’ for up to ~5 TeV with 300fb-1

  23. 4 TeV 6 TeV ATLAS W(1) Searches TeV-1 searches in lepton+MET • Feasibility using fast simulation for • Search for a peak in MT(ln) • Analysis challenges: • MET measurement, • for muons, the edge washed out. • In 100 fb-1 • detect a peak, if MC(= R-1)<6 TeV • fermionic couplings measured, if MC <~ 5 TeV • If none observed, • use -ve interference with SM W (en only) • a limit of MC < 11.7 TeV Polesello, Patra EPJ Direct C 32 Sup.2 (04) ED@LHC

  24. SM particles propagate in bulk with 1 ED KK-parity conservation Leads to stable LKP as DM candidate Pair of KK modes, no virtual KK modes  Limits are weaker due to small cross sections 600 570 g1 1 Q1 Z1 L1 Minimal Universal ED ED@LHC CMS g1g1/G1Q1/Q1Q1 analysis: • 4 low-pT isolated leptons (2 pairs of OS same flavour) l + m jets (m=4,3,2) + MET (from 2 undetectedg1) • Irreducible background: tt + m jets, 4 b-jets, ZZ, Zbb • Poisson-based significance estimator • Discovery reach: MC ~600 GeV for 1 fb-1 LEP + TeVatron limits: MC > 300-400 GeV

  25. Beauchemin, Azuelos ATL-PHYS-PUB-2005-003 Signal BG MKK=1.3TeV 200 600 1000 1400 MET (GeV) Thick brane Universal ED • Thick brane solutions: One UED embedded in (SUSY) LED • Gravity-matter interactions break PKK • Pair of KK partons decaying to SM parton+graviton: g1/g1->q/g+G • Measure excess of dijets with large MET • Main backgrounds: dijets + Z/W decaying invisibly • Fast simulation+SHERPA ED@LHC Sensitivity: • if MC = 1.3 TeV, clear probing with 6 pb-1 • 5σ up to 2.7 TeV with 100 fb-1

  26. q Q q Z 1 1 ( ) ~ ± l near c 0 m l 2 ( ) 1 ~ m l far g m l 1 ~ c 0 1 Is it SUSY or UED? SUSY ~ ED@LHC UED Matchev Cascade decays: how to separate? • Look for 2nd level KK modes (SUSY has none) - might be too heavy to observe • UED KK states are same spin of SM states (SUSY are not) - use dilepton invariant mass - use asymmetry in lq mass • use q or qbar, near and far lepton invariant mass • Success of method SUSY point dependent • Expected to work at 100-150 fb-1 (A. Barr)

  27. J Aguilar Is it a Z’ or RS Graviton? ED@LHC Handles: • Mass of resonance  little info about models (unless blessed enough to observe series of KK bumps) • Cross section  info about couplings • Branching fractions  test couplings & universality (G has well-defined ratio between ll/gg/ZZ and Z’ has no gg coupling ) • Angular distribution/asymmetries  spin and couplings (even then various Z’ are not easy to tell)

  28. Current favourite model building in warped space Gauge hierarchy problem, unification Fermion masses (localizations in the bulk) Dark Matter candidate, “LZP” Ingredients of model building: Originally: RS+SO(10) (Servant&Agashe,hep-ph/0411254), heavy bR (~1.5 TeV) and LZP Revised models: embed into SU(2)LxSU(2)RxU(1) (hep-ph/0612048) Additional custodial symmetry in SU(2)LxSU(2)R to protect EW observables (Z→bb) Light degenerate KK fermions (“custodians”) with no zero modes bR,L,Q = 2/3, -1/3, 5/3 RS with Custodial Symmetryhep-ph/0701158 (Dennis, MKU, Tseng [Ox], Servant [CERN/Saclay]) ED@LHC • Strategy: • Feasibility of KK quarks searches and related signatures through multi-W events of bR decays • Uncommon in SUSY searches • Stay as inclusive as possible

  29. Strong interaction pair production dominates (focus in bR – others the same, only enhanced EWK) Signature: 4W + 2b-jets Production & Decay ED@LHC • Decay channels: tW, bZ, bH • If H heavy enough, H→WW can give same signature (not simulated) • Simulate only tW decay modes of bR (Q=-1/3) • Scale up by 2(1+B2)/B2 for total rate including q5/3 (B(q5/3 tW) =1.0

  30. Multi-W Signature ED@LHC • Background Generic form: n×W + m×[b-jets] + k× [X] • In just 10fb-1 of data: • ~5300 tW from bR at 500 GeV • ~22000 tW from q5/3 at 500 GeV • Count Ws in leptonic and hadronic decays

  31. Generator-based: Calchep 2.4.3 + Pythia (CTEQ6L) Hadronic jets: Use (non-n) particles within |η|<4.9, with a seed of pT>1 GeV Softer tracks added if within ΔR<0.4 of jet centroid b-jets: hadronic jet closest to generated b Background sample tt (TopRex+Pythia), also some ttH (Pythia) Trigger Requirements follow standard leptonic W e or μ, pT > 25 GeV, |η|<2.4 MET > 20 GeV After trigger, require W pT > 150 GeV and jet pT>20 GeV Signal has 4 hadronic Ws from probably semileptonic quark decays Feasibility Study ED@LHC Require ΣET>800 GeV, for M(bR) = 500GeV

  32. Reconstruct W→jj: Loop over dijet pairs (no leptons) Add 4-vectors, assuming zero jet mass (might be an issue at high bR mass) 1 W already identified by its lepton Typical SM events have 2 Ws (or Zs) Eliminate one Whad: When looping over dijets, start from the highest-energy jet If with another jet, matches a W mass (70-90 GeV), start plotting with next pair Remaining W’s are mostly from non-SM sources Counting Hadronic Ws & Distinguishing Multi-W Signal b-tagging eliminates shoulder ED@LHC

  33. Present analysis feasibility study promising: Need more realistic simulation, 1st steps in ATLAS’s Atlfast following a bR mass scan Relating size of W peak to cross section is non-trivial Could suppress SM backgrounds by tighter/additional requirements Multi-W/Z events are generally interesting Identification using single-jet mass (e.g., Skiba&Tucker-Smith, hep-ph/0701247) q5/3 analysis: the smoking gun Identifying q5/3 would be a telltale indication for this model Possible analysis (looking into this right now): Select same-sign dilepton events Exclusively reconstruct bR on other side (similar to ATLAS TDR of 4th gen. quarks) Exotic, long-lived quarks – CHAMP signatures Next Steps ED@LHC Signature depends on t’L lifetime: either a possible CHAMP or LZP with 4W + 2b-jets + MET signature

  34. ED spectra is much colorful now than a few years ago. If ED exists at the TeV scale, we will be able to observe inclusive signatures above the SM background and carry out exclusive studies with few fb-1 data. CMS and ATLAS reaches for KK resonances are similar. With < 60 fb-1 LHC is expected to completely cover the RS1 region of interest. Blackholes may be the “smoking gun” from early data… Conclusions ED@LHC “How do we know what IT is?” “I’ll worry about this after something is discovered” I. Hinchliffe

  35. BACKUP ED@LHC

  36. ED@LHC

  37. ATLAS CMS Air-core toroids + solenoid in inner cavity 4 magnets Calorimeters in field-free region Solenoid Only 1 magnet Calorimeters inside field MAGNET (S) Si pixels + strips No particle identification B=4T s/pT ~ 1.5x10-4 pT  0.005 Si pixels+ strips TRT  particle identification B=2T s/pT ~ 5x10-4 pT  0.01 TRACKER Pb-liquid argon s/E ~ 10%/E uniform longitudinal segmentation PbWO4 crystals s/E ~ 2-5%/E no longitudinal segm. EM CALO Fe-scint. + Cu-liquid argon (10 l) s/E ~ 50%/E  0.03 Cu-scint. (> 5.8 l +catcher) s/E ~ 100%/E  0.05 HAD CALO Air s/pT ~ 7 % at 1 TeV standalone Fe s/pT ~ 5% at 1 TeV combining with tracker MUON Comparisons of Detectors ED@LHC F. Gianotti, Ichep06

  38. LKP LZP LSP Dirac fermion gauge boson Majorana fermion Z3 KK parity R parity ~ 600GeV – 1000GeV ~ 20GeV – Few TeV ~ 50GeV – 1TeV • LHC • Indirect(Astro) • LHC • Direct(Astro) • Indirect(Astro) • LHC • Indirect(Astro) L?P Dark Matter Candidates nature ED@LHC symmetry mass detection

  39. Experimental Bounds on MD [TeV] at 95% CL ED@LHC Karina F. Loureiro, C2CR07

  40. Assuming MPl(4+n) ~ mEW, with mEW being the only short distance scale in theory, and following the gravitational potential given by Gauss’ law in (4+n) dimensions we obtain that the size of the ED: LED Compactification Radius • For n=1 R~1013 cm: deviations of Newtonian gravity over solar system distances; empirically excluded. • For n>2, gravity modified noticeable at distances smaller than currently probed experimentally. • For n=2 (R~ 100m - 1mm) rather R < 44m; experimental evidence is within our reach. • A (4+n) dimensional graviton and other non SM fields will propagate into the bulk. • SM fields remain localized* within the thickness of the 3-brane. ED@LHC Radius of Compactified Dimensions Number of ED Karina F. Loureiro, C2CR07

  41. Tevatron Attempts for Signature Based Analysis ED@LHC

  42. Gokhan Unel, Athens07 RS ED & Z(n) ED@LHC

  43. ED@LHC • σ(pT) / pT • COT alone : 0.15% pT [GeV/c]-1 • COT + SVX + ISL: 0.07% pT [GeV/c]-1 • COT beam constrained: 0.05% pT [GeV/c]-1 • σ(d0): SVX+ISL: 40m including ~30m from beamline. • CEM cal: σ(E)/E = 13.5% / sqrt(E * sin(q)) • CHA cal: σ(E)/E = 50% / sqrt(E) [GeV] • Plug EM cal: σ(E)/E = 14.4% / sqrt(E) (+) 0.7%

More Related